The use of gaskets in sealing applications is commonplace in many industries. A well known application for gaskets is to provide fluid sealing between two mating surfaces such as between two ends of adjoining pipes or conduits where they are commonly in the form of a flange joint for ease of assembly and disassembly and for better sealing. A flange joint sealing gasket usually comprises a compressible ring defining an aperture of a size that matches the conduit being sealed and a body that matches the dimensions of the flange mating surfaces. In many applications however the flange joint mating surfaces which are typically metal eventually become damaged either by internal chemical corrosion, erosion or external weathering. This attrition of the surface can cause pitting, crevices and other imperfections to form on the surface. In such cases, replacement of an ordinary sealing gasket will not be sufficient to effect adequate sealing under operational pressures because the surface imperfections may provide fluid escape pathways and weak points in the surface sealing. As a consequence, it may become necessary to replace or repair the flanges or even the whole flanged pipe to reestablish or improve sealing performance.
In high pressure sealing applications, one preferred gasket has what is known as a Kammprofile core. This is effectively a gasket with a series of concentric serrations or a concertina-like profile on one or both facing surfaces. The profile is superimposed onto a solid core, usually metal, by the series of concentric serrations. During the sealing process the overlying softer sealing material is forced into the gaps between serrations to improve sealing by inducing stress concentrations on the sealing surfaces. The serrations also minimise lateral movement of the facing material, while the metal core provides rigidity and blowout resistance. Such a profile gives the gasket added strength for high pressure applications. As mentioned, such a gasket also includes a suitable compressible sealing material that is coated over the Kammprofile core. However, in cases of mating surfaces which have become pitted or corroded even such high pressure gaskets cannot always provide adequate sealing. It is an object of the present invention to provide an improved gasket suitable for such applications but also having wider applications for corroded or otherwise damaged mating surfaces.
U.S. Pat. No. 6,092,811 relates to a corrugated gasket core that uses inner and outer laminate materials. The inner material is designed to be chemically resistant to protect the outer material from chemical attack. The use of these gaskets to seal parallel mating surfaces including scratched or pitted surfaces is discussed but no mention of including a chemical treatment agent into the material or the possibility of simultaneously chemically protecting the damaged surfaces of the gaskets is mentioned.
Methods of coating the inner edge of a gasket with another sealing material usually a polymer or inorganic sealant are described in U.S. Pat. No. 6,093,467, US 2004/0007828 and US 2003/0230856. The possibility of the polymeric coating being of a greater depth to enhance sealing is disclosed as is the possibility of use with a damaged surface. However, no mention of chemically protecting the mating surfaces is mentioned.